The U. Chicago Medical Scientist Training Program submits this renewal application to the National Institutes of Health to continue and expand into the next century its training of outstanding leaders in the biomedical field. We request funding for 48 MSTP positions, an increase of 4 from the currently recommended slots (44 recommended/36 funded). At the requested level of support, NIH funding will cover approximately 25% of the program's costs, the rest being provided by institutional resources. We plan to recruit matriculating classes of 12 students who are expected to graduate in 8 years. The Medical Scientist Training Program at the U. Chicago Pritzker School of Medicine has been in existence for 37 years with uninterrupted funding and a superb training record of academic physicians in leadership positions (including directorships of MSTPs at UCSF and Harvard). It has graduated 193 students who have published over 1500 papers. Currently 68 individuals are enrolled in the program including 6% URM and 30% women. In the last five years, 34 students graduated from the Program and 38 students entered it. Continuing in the tradition of its graduates, our current MSTP students have published extensively in top journals such as Nature, Science, Cell, Immunity, Journal of Biological Chemistry, and others. In this proposal we provide compelling and detailed evidence on the superb quality of our students and the rigorous training environment at Chicago which is uniquely configured to support interdisciplinary programs such as the MSTP.